The present invention relates to metal chelates of linear polymers of ferrocene and the use of such metal chelates in a hydroformylation process. The novel metal chelates are exceptionally stable catalysts at elevated reaction temperatures. Furthermore because of the highly linear nature of the ferrocene polymers used to prepare the catalysts, they are homogeneous under a wide variety of reaction conditions yet may be easily rendered insoluble for recovery purposes.
D. Seyferth and H. P. Withers in Journal of Organometallic Chemistry, 185, C1-5 (1980) disclosed certain mono- and bidentate ligands, including 1-diphenylarsino-1'-diphenylphosphinoferrocene. Also disclosed was the fact that phosphino- or arsinoferrocene polymers capped at one end with lithium and at the other end with an organic moiety can be prepared by reacting (1,1'-ferrocenediyl)phenylphosphine or (1,1'-ferrocenediyl)phenylarsine with a stoichiometric deficiency of an organolithium reagent. Subsequent efforts to produce high molecular weight polymeric materials by means of this process have resulted in oligomers of up to about five units but no higher polymeric materials have been observed.
The reaction of ferrocene with phenyldihalophosphines to produce polymeric products has been studied by C. U. Pittman, Jr., J. Pol. Sci. A-1, 5, 2927-2937 (1967), and E. W. Neuse et al., J. Macromol. Sci. (Chem) A-1, 3, 371-386 (1967). The polymers formed were of the formula: ##STR1## respectively.
The polymers formed were of relatively low molecular weight having number average molecular weights less than 4000 amu, and less than 6500 upon subfractionation. The polymers also were reported to contain cross-linking formed by the non-selective reaction of more than two phenyldihalophosphines with certain ferrocene moieties. The references further described "heteroannular polymerization", the process resulting from cleavage of ferrocene rings by the action of hydrogen chloride produced in situ and the subsequent incorporation of moieties other than ferrocene and phosphine into the polymer structure. The principal heteroannular moiety is cyclopentylene.
Polymers prepared according to the prior art processes by the Lewis acid-catalyzed polycondensation of ferrocene contained appreciable amounts of such cyclopentylene or related groups in the polymeric structure. The presence of such cyclopentylene groups in the polymer tends to reduce the polymer's thermal stability and otherwise deleteriously affect the polymer's qualities.
Recoverable hydroformylation catalysts proposed in the prior art include metal ions such as rhodium or cobalt ions supported by crystalline aluminosilicates as disclosed by U.S. Pat. No. 3,352,924. Further catalysts have included inert solids such as carbon, silica, metal oxides, etc. impregnated with certain rhodium complexes disclosed in U.S. Pat. No. 3,487,112.
In U.S. Pat. No. 4,045,493 high molecular weight polyarylene substrates containing diaryl or dialkyl phosphine groups as chelating sites are used to complex metal carbonyls such as cobalt, rhodium, ruthenium, osmium, iridium and iron carbonyls to produce heterogeneous hydroformylation catalysts.
Similarly, U.S. Pat. No. 4,098,727 discloses heterogeneous hydroformylation catalysts containing solid, insoluble polymer supports having functional groups such as amine, thiol, phosphine or arsine groups complexed with metals selected from those of Group VIII of the Periodic Table.
U.S. Pat. No. 3,239,569 discloses cobalt complexes of phosphine compounds and their suitability for use as catalysts in hydroformylation reactions. Included are complexes of polydentate phosphine ligands illustrated at column 3, lines 14-29.